Symbolism, Imagery, Allegory
These were only briefly mentioned in the novel, but that doesn’t mean they are unimportant. Memory holes are those things in the ground that the Party insists any scraps of paper get tossed into. They lead to a furnace. Let’s think about this for a second. Memory…furnaces…memory…are memories being burned here? Why yes, they are. By destroying paper, the Party destroys documents and therefore evidence of the past. Which, given all the thought control going on, would seem to be the only real link left to history. Well, it was, anyway, until it got sent to the furnace.